Work

Characterization of KPC-287 conferring high-level ceftazidime–avibactam resistance in an ST11-KL64 Klebsiella pneumoniae isolate

Year: 2026

Type: article

Abstract: Background Klebsiella pneumoniae is a major global public health threat because of its increasing antimicrobial resistance and capacity for dissemination. Ceftazidime-avibactam (CAZ/AVI) is a key therapeutic option for infections caused by KPC-producing Enterobacterales , but emerging KPC variants compromises its efficacy. Here, we characterized multidrug-resistant K. pneumoniae isolate KP22-83 and investigated the contribution of KPC-287 to antimicrobial resistance, bacterial fitness, and virulence. Methods KP22-83 was characterized by antimicrobial susceptibility testing, whole-genome sequencing, resistance and virulence gene annotation, KPC phylogenetic analysis, and structural analysis. The bla KPC-287 gene was cloned into pUC19 and introduced into Escherichia coli DH5α and K. pneumoniae ATCC 13883 for functional validation. Growth, motility, in vitro competition, and biofilm formation assays were performed to evaluate fitness-associated phenotypes associated with KPC-287 carriage. The transferability and retention of bla KPC-287 were examined by conjugation assay and serial passage with or without CAZ/AVI. Virulence was evaluated using a Galleria mellonella infection model. Results KP22-83 belonged to ST11-KL64 and exhibited multidrug-resistance. Whole-genome sequencing identified bla KPC-287 together with 11 additional antimicrobial resistance-associated genes and 34 virulence-associated genes. KPC-287 clustered close to KPC-155 and differed by P168Q and A242del while retaining a highly conserved predicted global fold. Introduction of pUC19-KPC-287 increased the CAZ/AVI MIC to 64/4 mg/L in both E. coli DH5α and K. pneumoniae ATCC 13883, demonstrating that bla KPC-287 conferred high-level CAZ/AVI resistance. In contrast, meropenem MICs were not substantially altered. KPC-287 carriage caused modest reductions in growth, motility, and competitive fitness, together with greater crystal violet-stained biofilm biomass than the corresponding empty-vector controls. The bla KPC-287 was detected in transconjugants together with IncFII and IncR replicon markers and remained detectable after 30 passages with or without CAZ/AVI. Furthermore, KP22-83 caused substantial larval mortality, whereas KPC-287 acquisition did not markedly affect virulence in K. pneumoniae ATCC 13883. Conclusion This study provides a systematic functional characterization of KPC-287 in an ST11-KL64 K. pneumoniae clinical isolate in China. KPC-287 confers high-level CAZ/AVI resistance with limited fitness cost and bla KPC-287 is transferable in an IncFII/IncR plasmid background and remains detectable during serial passage. These findings highlight the need for continuous genomic surveillance and functional characterization of emerging KPC variants.

Source: Frontiers in Microbiology

DOI: 10.3389/fmicb.2026.1938185